Commit 2c140a24 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Mike Snitzer

dm: allow remove to be deferred

This patch allows the removal of an open device to be deferred until
it is closed.  (Previously such a removal attempt would fail.)

The deferred remove functionality is enabled by setting the flag
DM_DEFERRED_REMOVE in the ioctl structure on DM_DEV_REMOVE or
DM_REMOVE_ALL ioctl.

On return from DM_DEV_REMOVE, the flag DM_DEFERRED_REMOVE indicates if
the device was removed immediately or flagged to be removed on close -
if the flag is clear, the device was removed.

On return from DM_DEV_STATUS and other ioctls, the flag
DM_DEFERRED_REMOVE is set if the device is scheduled to be removed on
closure.

A device that is scheduled to be deleted can be revived using the
message "@cancel_deferred_remove". This message clears the
DMF_DEFERRED_REMOVE flag so that the device won't be deleted on close.
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 7833b08e
......@@ -57,7 +57,7 @@ struct vers_iter {
static struct list_head _name_buckets[NUM_BUCKETS];
static struct list_head _uuid_buckets[NUM_BUCKETS];
static void dm_hash_remove_all(int keep_open_devices);
static void dm_hash_remove_all(bool keep_open_devices, bool mark_deferred, bool only_deferred);
/*
* Guards access to both hash tables.
......@@ -86,7 +86,7 @@ static int dm_hash_init(void)
static void dm_hash_exit(void)
{
dm_hash_remove_all(0);
dm_hash_remove_all(false, false, false);
}
/*-----------------------------------------------------------------
......@@ -276,7 +276,7 @@ static struct dm_table *__hash_remove(struct hash_cell *hc)
return table;
}
static void dm_hash_remove_all(int keep_open_devices)
static void dm_hash_remove_all(bool keep_open_devices, bool mark_deferred, bool only_deferred)
{
int i, dev_skipped;
struct hash_cell *hc;
......@@ -293,7 +293,8 @@ static void dm_hash_remove_all(int keep_open_devices)
md = hc->md;
dm_get(md);
if (keep_open_devices && dm_lock_for_deletion(md)) {
if (keep_open_devices &&
dm_lock_for_deletion(md, mark_deferred, only_deferred)) {
dm_put(md);
dev_skipped++;
continue;
......@@ -450,6 +451,11 @@ static struct mapped_device *dm_hash_rename(struct dm_ioctl *param,
return md;
}
void dm_deferred_remove(void)
{
dm_hash_remove_all(true, false, true);
}
/*-----------------------------------------------------------------
* Implementation of the ioctl commands
*---------------------------------------------------------------*/
......@@ -461,7 +467,7 @@ typedef int (*ioctl_fn)(struct dm_ioctl *param, size_t param_size);
static int remove_all(struct dm_ioctl *param, size_t param_size)
{
dm_hash_remove_all(1);
dm_hash_remove_all(true, !!(param->flags & DM_DEFERRED_REMOVE), false);
param->data_size = 0;
return 0;
}
......@@ -683,6 +689,9 @@ static void __dev_status(struct mapped_device *md, struct dm_ioctl *param)
if (dm_suspended_md(md))
param->flags |= DM_SUSPEND_FLAG;
if (dm_test_deferred_remove_flag(md))
param->flags |= DM_DEFERRED_REMOVE;
param->dev = huge_encode_dev(disk_devt(disk));
/*
......@@ -832,8 +841,13 @@ static int dev_remove(struct dm_ioctl *param, size_t param_size)
/*
* Ensure the device is not open and nothing further can open it.
*/
r = dm_lock_for_deletion(md);
r = dm_lock_for_deletion(md, !!(param->flags & DM_DEFERRED_REMOVE), false);
if (r) {
if (r == -EBUSY && param->flags & DM_DEFERRED_REMOVE) {
up_write(&_hash_lock);
dm_put(md);
return 0;
}
DMDEBUG_LIMIT("unable to remove open device %s", hc->name);
up_write(&_hash_lock);
dm_put(md);
......@@ -848,6 +862,8 @@ static int dev_remove(struct dm_ioctl *param, size_t param_size)
dm_table_destroy(t);
}
param->flags &= ~DM_DEFERRED_REMOVE;
if (!dm_kobject_uevent(md, KOBJ_REMOVE, param->event_nr))
param->flags |= DM_UEVENT_GENERATED_FLAG;
......@@ -1469,6 +1485,14 @@ static int message_for_md(struct mapped_device *md, unsigned argc, char **argv,
if (**argv != '@')
return 2; /* no '@' prefix, deliver to target */
if (!strcasecmp(argv[0], "@cancel_deferred_remove")) {
if (argc != 1) {
DMERR("Invalid arguments for @cancel_deferred_remove");
return -EINVAL;
}
return dm_cancel_deferred_remove(md);
}
r = dm_stats_message(md, argc, argv, result, maxlen);
if (r < 2)
return r;
......
......@@ -49,6 +49,11 @@ static unsigned int _major = 0;
static DEFINE_IDR(_minor_idr);
static DEFINE_SPINLOCK(_minor_lock);
static void do_deferred_remove(struct work_struct *w);
static DECLARE_WORK(deferred_remove_work, do_deferred_remove);
/*
* For bio-based dm.
* One of these is allocated per bio.
......@@ -116,6 +121,7 @@ EXPORT_SYMBOL_GPL(dm_get_rq_mapinfo);
#define DMF_DELETING 4
#define DMF_NOFLUSH_SUSPENDING 5
#define DMF_MERGE_IS_OPTIONAL 6
#define DMF_DEFERRED_REMOVE 7
/*
* A dummy definition to make RCU happy.
......@@ -299,6 +305,8 @@ static int __init local_init(void)
static void local_exit(void)
{
flush_scheduled_work();
kmem_cache_destroy(_rq_tio_cache);
kmem_cache_destroy(_io_cache);
unregister_blkdev(_major, _name);
......@@ -404,7 +412,10 @@ static void dm_blk_close(struct gendisk *disk, fmode_t mode)
spin_lock(&_minor_lock);
atomic_dec(&md->open_count);
if (atomic_dec_and_test(&md->open_count) &&
(test_bit(DMF_DEFERRED_REMOVE, &md->flags)))
schedule_work(&deferred_remove_work);
dm_put(md);
spin_unlock(&_minor_lock);
......@@ -418,14 +429,18 @@ int dm_open_count(struct mapped_device *md)
/*
* Guarantees nothing is using the device before it's deleted.
*/
int dm_lock_for_deletion(struct mapped_device *md)
int dm_lock_for_deletion(struct mapped_device *md, bool mark_deferred, bool only_deferred)
{
int r = 0;
spin_lock(&_minor_lock);
if (dm_open_count(md))
if (dm_open_count(md)) {
r = -EBUSY;
if (mark_deferred)
set_bit(DMF_DEFERRED_REMOVE, &md->flags);
} else if (only_deferred && !test_bit(DMF_DEFERRED_REMOVE, &md->flags))
r = -EEXIST;
else
set_bit(DMF_DELETING, &md->flags);
......@@ -434,6 +449,27 @@ int dm_lock_for_deletion(struct mapped_device *md)
return r;
}
int dm_cancel_deferred_remove(struct mapped_device *md)
{
int r = 0;
spin_lock(&_minor_lock);
if (test_bit(DMF_DELETING, &md->flags))
r = -EBUSY;
else
clear_bit(DMF_DEFERRED_REMOVE, &md->flags);
spin_unlock(&_minor_lock);
return r;
}
static void do_deferred_remove(struct work_struct *w)
{
dm_deferred_remove();
}
sector_t dm_get_size(struct mapped_device *md)
{
return get_capacity(md->disk);
......@@ -2894,6 +2930,11 @@ int dm_suspended_md(struct mapped_device *md)
return test_bit(DMF_SUSPENDED, &md->flags);
}
int dm_test_deferred_remove_flag(struct mapped_device *md)
{
return test_bit(DMF_DEFERRED_REMOVE, &md->flags);
}
int dm_suspended(struct dm_target *ti)
{
return dm_suspended_md(dm_table_get_md(ti->table));
......
......@@ -128,6 +128,16 @@ int dm_deleting_md(struct mapped_device *md);
*/
int dm_suspended_md(struct mapped_device *md);
/*
* Test if the device is scheduled for deferred remove.
*/
int dm_test_deferred_remove_flag(struct mapped_device *md);
/*
* Try to remove devices marked for deferred removal.
*/
void dm_deferred_remove(void);
/*
* The device-mapper can be driven through one of two interfaces;
* ioctl or filesystem, depending which patch you have applied.
......@@ -158,7 +168,8 @@ void dm_stripe_exit(void);
void dm_destroy(struct mapped_device *md);
void dm_destroy_immediate(struct mapped_device *md);
int dm_open_count(struct mapped_device *md);
int dm_lock_for_deletion(struct mapped_device *md);
int dm_lock_for_deletion(struct mapped_device *md, bool mark_deferred, bool only_deferred);
int dm_cancel_deferred_remove(struct mapped_device *md);
int dm_request_based(struct mapped_device *md);
sector_t dm_get_size(struct mapped_device *md);
struct dm_stats *dm_get_stats(struct mapped_device *md);
......
......@@ -267,9 +267,9 @@ enum {
#define DM_DEV_SET_GEOMETRY _IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl)
#define DM_VERSION_MAJOR 4
#define DM_VERSION_MINOR 26
#define DM_VERSION_MINOR 27
#define DM_VERSION_PATCHLEVEL 0
#define DM_VERSION_EXTRA "-ioctl (2013-08-15)"
#define DM_VERSION_EXTRA "-ioctl (2013-10-30)"
/* Status bits */
#define DM_READONLY_FLAG (1 << 0) /* In/Out */
......@@ -341,4 +341,15 @@ enum {
*/
#define DM_DATA_OUT_FLAG (1 << 16) /* Out */
/*
* If set with DM_DEV_REMOVE or DM_REMOVE_ALL this indicates that if
* the device cannot be removed immediately because it is still in use
* it should instead be scheduled for removal when it gets closed.
*
* On return from DM_DEV_REMOVE, DM_DEV_STATUS or other ioctls, this
* flag indicates that the device is scheduled to be removed when it
* gets closed.
*/
#define DM_DEFERRED_REMOVE (1 << 17) /* In/Out */
#endif /* _LINUX_DM_IOCTL_H */
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